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Currently if you ifconfig down a vtnet interface while it is being used via netmap, the kernel panics due to trying to treat the cookie values in the virtio rings as mbufs to be freed. When netmap is enabled, these cookie values are pointers to something else. Note that other netmap-aware drivers don't seem to need this as they store the mbuf pointers in the software rings that mirror the hardware descriptor rings, and since netmap doesn't touch those, the software state always has NULL mbuf pointers causing the loops to free mbufs to not do anything. However, vtnet reuses the same state area for both netmap and non-netmap mode, so it needs to explicitly avoid looking at the rings and treating the cookie values as mbufs if netmap is enabled. Differential Revision: https://reviews.freebsd.org/D2348 Reviewed by: adrian, bryanv, luigi MFC after: 1 week Sponsored by: Norse Corp, Inc.
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